Method of fabricating a gate cut feature for multi-gate semiconductor devices

Abstract

A method includes forming a fin protruding from a substrate, forming a first dielectric feature adjacent to the fin over the substrate, forming a cladding layer over the fin and the first dielectric feature, and removing a portion of the cladding layer to form an opening. The opening exposes the first dielectric feature. The method further includes forming a second dielectric feature adjacent to the cladding layer, the second dielectric feature filling the opening, forming a dummy gate stack over the fin and the second dielectric feature, forming source/drain (S/D) features in the fin adjacent to the dummy gate stack, and replacing the dummy gate stack and the cladding layer with a metal gate stack. The second dielectric feature divides the metal gate stack.

What is claimed is: 
     
       1. A method, comprising:
 forming a fin protruding from a substrate; 
 forming a first dielectric feature adjacent to the fin over the substrate; 
 forming a cladding layer over the fin and the first dielectric feature; 
 removing a portion of the cladding layer to form an opening, wherein the opening exposes the first dielectric feature; and 
 forming a second dielectric feature adjacent to the cladding layer, wherein the second dielectric feature fills the opening; 
 forming a dummy gate stack over the fin and the second dielectric feature; 
 forming source/drain (S/D) features in S/D regions of the fin not covered by the dummy gate stack; 
 removing the dummy gate stack to form a gate trench, the gate trench exposing the cladding layer; 
 removing the cladding layer; and 
 forming a metal gate stack in the gate trench, wherein the second dielectric feature divides the metal gate stack. 
 
     
     
       2. The method of  claim 1 , wherein the removing of the portion of the cladding layer forms the opening defined by a width that is less than a width of the second dielectric feature. 
     
     
       3. The method of  claim 1 , wherein the removing of the portion of the cladding layer forms the opening defined by a width equals to a width of the second dielectric feature. 
     
     
       4. The method of  claim 1 , wherein the metal gate stack has a top surface coplanar with a top surface of the second dielectric feature. 
     
     
       5. The method of  claim 1 , further comprising:
 forming a dielectric helmet ( 214 ) over the second dielectric feature, wherein the dielectric helmet separates a top portion of the metal gate stack. 
 
     
     
       6. The method of  claim 1 , further comprising:
 forming a third dielectric feature disposed on an opposite side of the fin away from the second dielectric feature, wherein the third dielectric feature is disposed over the cladding layer without an opening to expose the first dielectric feature, and wherein the cladding layer under the third dielectric feature is replaced by the metal gate stack without being separated by the third dielectric feature. 
 
     
     
       7. The method of  claim 6 , wherein a portion of the metal gate stack is disposed over the third dielectric feature. 
     
     
       8. A method of forming a semiconductor structure, comprising:
 forming a first fin and a second fin disposed over a substrate, wherein each of the first and the second fins includes alternating channel layers and non-channel layers; 
 forming an isolation feature between the first fin and the second fin over the substrate; 
 forming a cladding layer over the first fin, the second fin, and the isolation feature; 
 forming an opening in the cladding layer over the isolation feature, thereby separating the cladding layer into a first portion over the first fin and a second portion over the second fin; 
 forming a gate cut feature between the first portion and the second portion of the cladding layer, thereby filling the opening; 
 forming a dummy gate stack over the first fin, the second fin, and the gate cut feature; 
 forming source/drain (S/D) features in regions of the first and second fins not covered the dummy gate stack; 
 removing the dummy gate stack to form a gate trench, the gate trench exposing the cladding layer; 
 removing the cladding layer to expose sidewalls of the non-channel layers in the gate trench; 
 removing the non-channel layers; and 
 forming a metal gate stack in the gate trench, wherein the gate cut feature truncates the metal gate stack into two portions disposed on opposite sides of the gate cut feature. 
 
     
     
       9. The method of  claim 8 , wherein the forming of the opening in the cladding layer removes an entire horizontal portion of the cladding layer between the first and the second fin. 
     
     
       10. The method of  claim 8 , wherein the forming of the opening in the cladding layer removes a portion of a horizontal portion of the cladding layer between the first and the second fin. 
     
     
       11. The method of  claim 8 , wherein the isolation feature includes a material that is the same as a material included in the gate cut feature. 
     
     
       12. The method of  claim 8 , wherein the metal gate stack has a top surface coplanar with a top surface of the gate cut feature. 
     
     
       13. The method of  claim 8 , further comprising:
 forming a dielectric helmet over the gate cut feature, wherein the dielectric helmet cuts the metal gate stack into two portions disposed on opposite sides of the dielectric helmet. 
 
     
     
       14. The method of  claim 8 , further comprising:
 forming a third fin disposed over the substrate, wherein the first fin and the third fin are disposed on opposite sides of the second fin; and 
 forming a dummy gate cut feature between the second and the third fin, wherein a third portion of the cladding layer over the third fin is connect to the second portion of the cladding layer, and wherein the metal gate stack under the dummy gate cut feature is continuous. 
 
     
     
       15. The method of  claim 14 , wherein a portion of the metal gate stack spans across the second fin, the dummy gate cut feature, and the third fin. 
     
     
       16. A method, comprising:
 forming a fin over a substrate, the fin including alternating channel layers and sacrificial layers; 
 depositing an isolation feature on sidewalls of the fin; 
 forming a cladding layer over the sidewalls of the fin and a top surface of the isolation feature; 
 forming an isolation structure over a horizontal portion of the cladding layer, wherein the fin and the isolation structure sandwich a vertical portion of the cladding layer, wherein a top surface of the vertical portion of the cladding layer is not covered by the isolation structure; 
 removing the vertical portion and the horizontal portion of the cladding layer to form a trench, the trench exposing sidewalls of the sacrificial layers, a bottom portion of the trench extending to a position directly under the isolation structure; 
 removing the sacrificial layers; and 
 forming a metal gate structure in the trench, the metal gate structure wrapping around each of the channel layers, wherein a portion of the metal gate structure filling the bottom portion of the trench is directly under the isolation structure. 
 
     
     
       17. The method of  claim 16 , wherein, in a cross section perpendicular to a lengthwise direction of the channel layers, the metal gate structure fully surrounds the isolation structure. 
     
     
       18. The method of  claim 16 , further comprising:
 forming an opening in the horizontal portion of the cladding layer, wherein the isolation structure extends downwardly through the opening and has a physical contact with the top surface of the isolation feature. 
 
     
     
       19. The method of  claim 18 , further comprising:
 recessing the metal gate structure, such that a top surface of the metal gate structure is lower than a top surface of the isolation structure. 
 
     
     
       20. The method of  claim 16 , further comprising:
 forming a dummy gate stack over the fin and the isolation structure; 
 patterning the dummy gate stack to form an opening directly above the isolation structure; 
 recessing the isolation structure through the opening; and 
 removing the dummy gate stack.